Enhanced Soft-magnetic Performance of Fe-based Composites Via Nanoparticle Doping and Hot-press Sintering for High-frequency Applications

Soft magnetic composites (SMCs) are vital in modern power electronics, including transformers, motors, and generators, where high permeability, low core loss, and high-frequency stability are critical. This chapter presents a comprehensive study on the structural and magnetic performance of FeSi-based and Fe/Fe₃O₄-based SMCs synthesised via the hot-press sintering technique, focusing on the influence of magnetic nanoparticle doping on their soft magnetic behaviour. In Fe–6.5 wt% Si/Fe₂O₃ SMCs, the incorporation of high-resistivity Fe₂O₃ nanoparticles effectively filled interparticle gaps and enhanced densification. All samples exhibit excellent effective permeability frequency stability, ranging from 10 kHz to 100 kHz. Furthermore, as the Fe2O3 content increased from 0 to 2 wt%, the effective permeability (μₑ) significantly improved from 22.32 to 30.45 (a 36.4% increase). Adding Fe2O3 nanopowders from 0–5 wt% also enhanced electrical resistivity from 29.55 to 50.70 mΩ.cm. This, in turn, decreased the value of Pe at f = 100 kHz and Bm=10 mT from 6.61 to 4.15 kW/cm3 (a 37.21% reduction), compared to undoped samples. Furthermore, as Fe2O3 content increases from 0 to 5 wt%, the power loss Pcv of the Fe2O3-doped Fe-6.5Si SMCs decreases from 25.63 kW/m3 to 16.13 kW/m3, a 37.0% reduction. Similarly, in Fe–6.5 wt% Si/(Fe: TiO₂) nanocomposites, with increased doping concentration of Fe nanopowder from 0 to 1.66 vol%, both the density and electrical resistivity significantly increased from 6.72 g/cm³ to 7.11 g/cm³ (up 5.78 %) and from 29. 36 mΩ.cm to 37.16 mΩ.cm, respectively. This can be attributed to reduced interparticle voids and carrier scattering. The value of saturation magnetisation (Ms) increased first from 180.89 emu/g to 189.5 emu/g as the Fe NP content increased from 0 to 1.66 vol%, reaching a maximum value of about 189.5 emu/g for a sample with 1.66 vol% of Fe nanopowder content. Furthermore, all the composites exhibit low coercivity (